Pollution or exhaust emission control devices are employed on motor vehicles to control atmospheric pollution. Types of devices currently in widespread use include sulfur traps, NOx adsorbers, catalytic converters and diesel particulate filters or traps. These types of devices contain a treatment element to control pollution. The treatment element in a catalytic converter, for example, can be a catalytic element, a substrate or a monolithic structure coated with a catalyst for the oxidation of pollutants and mounted in a housing. The treatment element can be mounted in a housing that often comprises a shell with end cone assemblies welded or otherwise attached to the ends of the housing for attachment to exhaust pipes or other exhaust components. The shell can be either circular or a suitable non-circular geometry.
End cone assemblies can be one piece or single end cone structures formed, for example, by spin forming techniques. Alternatively, end cone assemblies can be dual wall end cone assemblies comprising an inner cone and an outer cone. In such an assembly, the outer and inner end cones each typically have conical walls and comprise a large end for connecting to the housing or shell of the exhaust emission control device, and a small end for connecting with a pipe or other components of an automotive exhaust system. Between the inner cone and the outer cone is an insulating space. In previous dual wall end cone assemblies, such as that disclosed in U.S. Pat. No. 6,010,668 to Lawrence et al., the insulating space can contain an insulating material such as a fibrous insulating pad. While suitable for many applications, some disadvantages of this design include the high cost of the fibrous insulating material and difficulties in spin forming the end cones into non-circular cross sections.
There thus remains a need for improved end cone assemblies and exhaust emission control devices and methods of making exhaust emission control devices.